This invention relates to a solar screening and/or electrically heatable layered assembly employing a metal/dielectric stack and more particularly to such an assembly which includes an energy-absorbing plastic interlayer.
Metal/dielectric stacks in window applications to reflect infrared radiation while transmitting significant visible light are well known. The effect is to reduce temperature buildup from solar radiation within an area delimited by one or more of such windows. These stacks are called interference filters and comprise at least one layer of reflective metal sandwiched between reflection-suppressing or antireflective dielectric layers. Likewise known is heating the metal layer by electrical conductance to provide defrost or deice and/or defog capability. Representative structures for motor vehicle windshields are disclosed in International Publication No. W088/01230 and U.S. Pat. No. 4,799,745.
When such interference filters are combined with glass in laminated glazing assemblies, particularly in vehicle windshields, it is desirable to include a shock-dissipating interlayer of plasticized polyvinyl butyral (PVB) in the assembly to absorb a blow, e.g. from the head of an occupant within the vehicle, without penetrating the windshield. Various antireflective dielectric layers as components of the interference filter or metal/dielectric stack have been interchangably proposed for contact with such a PVB layer as, for example, recited in U.S. Pat. No. 4,786,783. Unfortunately, the integrity of multilayered laminated glazings which include such interference filters and PVB layers have been less then desirable after extended periods of use.